A residential solar array with battery storage and an electric vehicle, on Long Island, New York. This report covers the record through 7 September 2026. All measurements come from a local InfluxDB written by Home Assistant. Each figure is produced by a script, and the method and its limitations are stated with the result.
Nothing here updates automatically. The figures are fixed at the period stated above.
1. Delivered output against rated capacity
The array delivers 42% of what 36 panels rated 425 W would produce facing the sun squarely under a clear sky. Roof geometry accounts for 20.2 points of the shortfall, conversion and shading losses for 15.8, and weather, including panel temperature, for the remainder.
Measured daily generation against a clear-sky plane-of-array model for the four roof faces. The conversion band is the shortfall on the best days on record, which are cold and clear, so it excludes panel temperature.
2. Time-of-use credits cannot reach the discounted band
The utility's optional overnight rate discounts 10pm–6am and nets net-metering credits within bands rather than across them. Over the record the array exported 25 kWh into that band and imported 6,219 kWh from it; 754 kWh of credit would strand in bands with no remaining consumption to offset.
Grid meter split by band under each published rate. Federal holidays not modeled.
3. Generation offsets most, not all, of household load
Over the last twelve months the array generated 73% of household consumption. The house remains a net importer of 5,740 kWh. Vehicle charging is 22% concurrent with generation, but under flat-rate billing that is immaterial: the bill is struck on net import, so every additional kilowatt-hour consumed is one imported.
Counter series for load and grid flows; generation spans both eras. Concurrency measured in 15-minute bins.
4. Islanding duration exceeds utility outage duration
The system islanded 14 times, totalling 77 minutes, of which approximately 12 minutes are attributable to the utility. The remainder is the 300-second Enter Service delay required by IEEE 1547. No unintentional island is shorter than 300 seconds.
Gateway grid-status transitions, corroborated against grid power.
5. A nearby tree is measurable from generation data
A tall tree stands west of the house. Comparing generation at mirrored solar positions locates its upper edge at 35–40° elevation near azimuth 255°, implying a distance of roughly 80 feet for an 80-foot tree. Aerial imagery gives approximately 75 feet.
East and west output compared at matched solar elevation and azimuth offset.
6. A passing test admitted a 180-degree error
Solar azimuth was computed from south while documented as from north, placing the summer sun due north at local noon. The existing test asserted only that morning azimuths fall in (0°, 180°) and afternoon in (180°, 360°), which both conventions satisfy.
Detected when a panel-orientation fit returned a physically impossible result. Three absolute anchors were added.
The system owner has published periodic write-ups of this installation at evan.wtf. Result 2 restates a mechanism already described in the one-year write-up; what this report adds is the measurement.
Each page is a single HTML file containing its own data. No external resources are loaded.
Series are written on change, so a constant value produces no rows. Absence of data is not zero. Totals are computed by holding each reading until the next rather than by interpolating, and gaps longer than 30 minutes are not crossed. Daily figures record the number of samples they rest on and the fraction of the day observed; days the recorder did not cover are excluded rather than counted as zero.
Cumulative counters begin 19 May 2025, so daily totals cover a shorter span than the installation has run. Attribution of the vehicle's supply between sources is an estimate rather than a measurement and is described on that page. Federal holidays are not modeled in the time-of-use bands.
This report describes one installation. It is not a product comparison and contains no recommendation.